Lili RanaiseMBAKOP 1,2
1University of Yaounde I, Cameroon ; 2OCEAC.
CaHReF 2018, Yaoundé Congres hall, 08 – 11 January 2019 , OAU005
Background: Insecticide resistance is a real threat for the efficacy of insecticidal based strategies targeting major malaria vectors in Africa. Here we evaluate the evolution of the insecticide susceptibility phenotype of populations of A. gambiae in two environments under strong anthropogenic pressure in comparison with another environment with no significant changes.
Objectif: Describe the evolution of insecticide susceptibility in the main malaria vectors over three years of entomological monitoring in two equatorial locations with ongoing environmental changes.
Methodology: Larval collections were carried out between july 2014 and december 2017 in Nyabessan, Simbock and Olama. The two first localities are characterized by a new construction of large hydroelectric dam and ongoing urbanization respectively. The third site (Olama) belonging to the same ecological domain served as control arm because of their rural pattern with insignificant environmental changes. Insecticide resistance levels were measured on four days old mosquitoes by WHO sucseptibility tests with Deltamethrin with or without piperonyl butoxide (PBO) synergist, permethrin, DDT and Bendiocarb. The distribution of A. gambiae sub-species and pyrethroid target-site mutations (kdr) were investigated using molecular assays.
Results: Two species - A. coluzzi and A. gambiae ss - were identified in both study sites, with significant variations by years and locations. In Olama, A. gambiae ss. was the unique species found across the years. Mortality rates recorded in both study sites suggested high resistances in A. gambiae and A. coluzzii populations to DDT and pyrethroids, with variations of the frequency of 1014 F kdr resistant mutations from one year to another. However, these populations were fully susceptible to bendiocarb. Pre-exposure to PBO increased the restoration rate of susceptibility to pyrethroids, suggesting involvement of other mechanisms.
Conclusion/Recommandation: This study on the evolution of insecticide resistance patterns in A. gambiae ss. and A. coluzzii in locations with undergone anthropogenic changes, has provided further evidences that efficacy of insecticidal based control measures and strategies targeting malaria vectors may be affected by environmental changes in our study areas.
Key Words:insecticide resistance, A. gambiae., environmental changes